The invention relates to a novel method of driving an electronically directly driven focal-plane shutter.
In camera technology, a focal-plane shutter is an assembly which consists essentially of two motor-driven lightproof curtains. In the basic position, the first curtain is closed, and the second curtain is open. In order to take an exposure, the first curtain is opened, and then the second curtain is closed. The operating time of the shutter is the time it takes a curtain to move across the image field.
If it is desirable to achieve exposure times which are markedly shorter than the operating time of the curtains, it is necessary to begin closing the second curtain immediately after the first curtain starts to open. A slot is then formed, which runs across the image field. For example, in an exposure time of 1/4000 sec, a slot width of 2 mm is produced in a run length of 24 mm.
The operating sequences of the two curtains must therefore be as identical as possible, which can be achieved in mechanically driven shutters (e.g., driven by a spring loaded actuator, acting as a mechanical drive) by means of corresponding compensation measures.